package org.apache.lucene.index;

import java.io.IOException;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/** This is a {@link LogMergePolicy} that measures size of a
 *  segment as the number of documents (not taking deletions
 *  into account). */

public class LogDocMergePolicy extends LogMergePolicy {

    /** Default minimum segment size.  @see setMinMergeDocs */
    public static final int DEFAULT_MIN_MERGE_DOCS = 1000;

    public LogDocMergePolicy() {
        minMergeSize = DEFAULT_MIN_MERGE_DOCS;

        // maxMergeSize(ForForcedMerge) are never used by LogDocMergePolicy; set
        // it to Long.MAX_VALUE to disable it
        maxMergeSize = Long.MAX_VALUE;
        maxMergeSizeForForcedMerge = Long.MAX_VALUE;
    }

    @Override
    protected long size(SegmentInfo info) throws IOException {
        return sizeDocs(info);
    }

    /** Sets the minimum size for the lowest level segments.
     * Any segments below this size are considered to be on
     * the same level (even if they vary drastically in size)
     * and will be merged whenever there are mergeFactor of
     * them.  This effectively truncates the "long tail" of
     * small segments that would otherwise be created into a
     * single level.  If you set this too large, it could
     * greatly increase the merging cost during indexing (if
     * you flush many small segments). */
    public void setMinMergeDocs(int minMergeDocs) {
        minMergeSize = minMergeDocs;
    }

    /** Get the minimum size for a segment to remain
     *  un-merged.
     *  @see #setMinMergeDocs **/
    public int getMinMergeDocs() {
        return (int) minMergeSize;
    }
}
